Burner safety control



Jan. 8, 1963 A. A. FENNELL BURNER SAFETY CONTROL INVENT R.

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Jan. 8, 1963 Filed July 19. 1957 A. A. FENNELL BURNER SAFETY. CONTROL 5Sheets-Sheet 2 7 w www Jan. 8, 1963 A. A. FENNELI.

BURNER SAFETY CONTROL 3 Sheets-Sheen'I 5 Filed July 19. 1957 ZEE INENTOR. f7 @d @fz/ze@ number of burners.

United States4 Patent 3,072,177 BURNER SAFETY CNTRUL Anthony A. Fennell,Homewood, lll. (379 E. 147th St., Harvey, Ill.) Filed July 19, 1957,Ser. No. 673,016 3 Claims. (El. 153-423) The present invention relatesto a novel control system, and more particularly to a novel systemadapted to control burners and the like.

Industrial furnaces are frequently provided with a plurality of burnerswhich utilize gas, oil or other suitable fuels. Some means must beprovided for shutting off all burners if any one of them goes out sothat unburned fuel is not introduced into the furnace from suchextinguished burners and subsequently ignited by one of the otherburners. It will be appreciated that fuel ignited in this manner mightwell cause an eXplosio-n. Various control systems have heretofore beenproposed, which systems usually incorporate a separate detector for eachburner capable of sensing the presence or absence of a flame, and aseparate control circuit for each detector.

`Such heretofore proposed control circuits are costly so that the costof a furnace installation is high especially when the furnace has aconsiderable number of burners.

An important object of the present invention is to provide a novelcontrol system for a plurality of burners, which system is materiallysimplified and eliminates duplication of many parts heretofore believedto be necessary so that the system may be installed and maintainedrelatively easily and economically.

A more specific object of the present invention is to provide a novelcontrol system of the above described type which utilizes separatedetectors or fiame sensing devices for each burner and which is greatlysimplified as compared with heretofore proposed systems in that itincludes only a single control circuit successively and separatelyconnectable with each of the detectors or sensing devices so as toaccomplish periodic inspection of each of the burners.

Still another object of the present invention is to provide a novelcontrol system of the type mentioned in the pre"eding paragraph which isconstructed so as to shut off the burners in the event of failure of thesystem to proceed with successive inspection of the burners.

Other objects and advantages of the present invention will becomeapparent from the following description and the accompanying drawingswherein- FIG. 1 is a schematic view showing a control systemincorporating features of the present invention;

PIG. 2 is a schematic view showing a slightly modified control system;

FIG. 3 is a schematic view showing another slightly modified form of thepresent invention;

FIG. 4 is a detailed diagrammatic showing of the fuel supply controlrelay employed in the system of FIG. 1;

FIG. 5 is a detailed diagrammatic showing of the sensing circuit relayincorporated in the modified control system of FIG. 2; and

FIG. 6 is a detailed diagrammatic showing of the pulse *timer employedin the modified form of the invention illustrated in FIG. 3.

In FIG. 1 there is shown a control system 10 for conv'trolling burners12, 14, 16, 18, 20 and 22 in a furnace or the like. While six burnershave been shown for the purpose of illustrating the present invention,it will be appreciated that the advantages of the present invention maybe realized when the control system is constructed for use with at leasttwo burners and any desired larger Fuel is supplied to the burners froma common pipe 24, and a valve 26 is connected in icc this pipe. Thisvalve is a spring biased solenoid operated valve of known constructionsuch that when the solenoid 28 thereof is energized the valve is ope-nand when the solenoid is deenergized spring means causes the valve toclose.

Adjacent the burners are detectors or sensing devices 30, 32, 34, 36, 38and 40. These detecting or sensing devices are of known construction andmay, for example, be of a type which generates an electric signal inrespense to heat or light from the flame when the burner is lit.Alternatively, the sensing or detecting devices may be of the resistancetype which changes electricity conducting characteristics in accordancewith temperature.

ln accordance with a feature of the present invention the control systemis provided with only a single relay 42 for controlling the fuel shutoff valve 26. The relay is preferably of a fast acting type and of knownconstruction and has terminals connected with the solenoid 28 by wires44 vand 46, Power is supplied to the relay through lines 48 and 50.Safety switch means generally designated by the numeral 52 is insertedin the line 50 for shutting olf power to the relay and thereby causingthe fuel shut off valve to close in the event of a failure of a portionof the control system as described more fully hereinbelow.

The control system is provided with switch means generally designated bythe numeral 54 for .successively and separately connecting each of thesensing devices Sil-4G with the relay 42. It will be appreciated thatthe switch means 54 may be constructed in various ways, but for thepurpose of illustrating the present invention the switch means 54 isprovided with a plurality of fixed switch contacts 56, 58, 60, 62, 64and 66 cooperable with movable contacts 68, 70, 72, 74, 76 and '78. Thefixed contacts are respectively connected with the relay by common wires80 and 82 and branch wires 84, 86, 88, 90, 92 and 94. The movablecontacts are respectively mounted on movable fingers 96, 98, 100, 102,104 and 1616 which are connected with one terminal of the sensingdevices 30-40 respectively by wires 108, 110, 112, 114, 116 and 118.Other terminals of the sensing devices are connected to the relay bywire and branch wires 122, 124, 126, 128, and 132.

Considering FIG. 4, the relay 42 will be seen to include a coil 200which is connected between line 48 and wire 80. Energization of coil 200causes a magnetic element 202 to operate a movable contact 204, contact2114 being electrically connected to both line 50 and wire 126. Relay 42also includes a fixed contact 2h63 and when magnetic element 292 directscontact 204 to make electrical connection with contact 206, a circuit iscompleted from line Sil, through the contacts 204 and 2l6-to wire 46,through solenoid 28 and through-wire 44 to line 48. As will berecognized, coil 201i remains energized to preserve completion of thecircuit through contacts 204 and 206 to the operating solenoid 23 ofvalve 26 only so long as switch means 54 and safety switch means 52continue the circuit from line Sil to wire 8% in a completed condition.

The switch means 54 is provided with a plurality of rotatable cams 134,136, 138, 140, 142 .and 144 respectively engageable with cani elements146?, 148, 150, 152, 154 and 156 on the fingers for positioning thefingers to open or close the switch contact points. The rotatable camsare all fixed on a shaft 158 which is continuously driven by an electricmotor 169. The rotatable cam members are constructed and fixed on theshaft 15S so that the pairs of switch contact points are successivelyopened and closed and so that only one pair of the contact points isclosed at one time to accomplish inspection of a given burner. Theconstruction may be such that there will be a slight overlapping of theperiods during which successive pairs of points are closed so as to pre`vent the relay from closing the shut off valve as the relay is switchedfrom one sensing device to the next. It will be appreciated that sincethe motor 161i) is continuously operated the cycle of opening andclosing of the switches will be continuously repeated. As a result eachof the detector devices4 will be connected periodically with the relay.

It will be appreciated that in the event one of the burners goes out,its associated sensing or detector device will signal the relay 42 uponbeing periodically connected with the relay so that the relay willfunction to close the valve 26. In order' to prevent an undue lapse oftime between the instant a burner goes out and the moment in which itsassociated sensing device is subsequently connected with the relay, itis necessary to rotate the cam shaft 158 ata speed which enables theentire cycle to be completed inA a relatively short time. While thistime interval may be varied somewhat for different installations, itshould beas short asl possible and as a result each burner will beinspected for no more than a few seconds during each scanning cycle.Thus the relay 42 must be a fast operating type which is capable ofcausing the fuel shut off valve to be closed upon receiving a briefsignal from one of the scanning devices and before the next scanningdevice is connected with the relay.

In the event of a failure of the motor 161B or some other mechanicalbreakdown which would cause the cam shaft 158 to stop it would bepossible for a single sensing or detector device to remain connectedwith the relay 42. Under such condition` it might be possible for aburner associated with another sensing device to go` out without beingdetected. However, in accordance with a feature of the present inventionthis possibility is eliminated by the provision ofthe above mentionedswitch means 52. In this embodiment, the switch means S2 has a fixedcontact 162 and a cooperable contact 16a which is axially movable on arotatably supported shaft 166. A y weight governor type device 168 isdriven by the shaft 166 for raising the contact 164 into engagement withthe contact 162. The shaft 166 is in turn driven from the cam shaft 158through bevel gears 178 and 172. Thus, in the event the cam shaft 158 isstopped for any reason, the shaft 166v will also be stopped and the flyweight device will cause thecontact 164` to be disengaged from thecontact 162. When thisoccurs power to the relay 42 is shut off and thefuel valve 26 is closed.

FIG. 2-shows a slightly modified form of the present invention which issimilar to the above described control system as indicatedI by theapplication of identical reference numerals with the suffix a added tocorresponding elements. Th's embodiment differs primarily in theconstruction of the safety switch means. More specifically, the safetyswitch means 52a` comprises a relay 174 for connecting portions of thewire 50a only when electricity is supplied for energizing the relaythrough the wires 176 and 178. These wires are connected with terminalsof a small generator 180 which is driven from the cam shaft 158a throughgears 170:1 and 172a. Thus, whenever the cam shaft 158a is stopped, thegenerator 180 is stopped so that the relay 174 is deenergized and therelay 42a is disconnected from the main power source.

With specific reference to FIG. 5, the relay 174V will bey seen toinclude a coil 288 which is-connected in electrical series circuit withgenerator 180 by the wires 176 and 178. The relay 174 also includes amagnetic element 210 which is controlled by the coil 208 to actuate amovable contact 212. The movable contact 212 is arranged to coact with afixed contact 214 in completing a circuit from linel 50a, through thecontacts 212 and 214 and through a wirer216- to the movable contact ofrelay 42a., As will be recognized, cessation of the operation ofgenerator 180 serves to deenergize coil 208 whereby tov open the circuitthrough contacts 212 and 214. 'Ihis in turn opens the circuit from line58a through the contacts of relay 42a to the line 48a.

FIG. 3 shows another slightly modified form of the present inventionwhich is similar to the above described structures as indicated by theapplication of identical reference numerals with the sufiix b added tocorresponding elements. This embodiment also differs primarily in theconstruction of the safety switch means 52b. In this embodiment theswitch means 52b comprises a pulse type or periodically energized timer182. Such timers are of known construction and usually include a holdingcircuit which must be periodically energized in order to prevent openingof the main power line contacts. In the present installation the timerholding circuit has terminals connected. by wires 184 and 186 to a fixedcontact 188 and a contact 190 on a movable finger 192. A cam 194 fixedon the cam shaft 158b is constructed so as to operate the movable finger192 to close the contacts 188 and 19t) periodically duringeach-revolution of the cam shaft. Thus, if for any reason the cam shaftis stopped the timer will not be periodically energized and it willfunctionto disconnect the relay 42h from the main power source.

Turning to FIG. 6 for a more detailed consideration of the pulse timer182, line 48b will be seen connected to wire 184Y through a coil 218 andto relay 42b through a fixed contact 228 and a movable contact 222. Coil21S operates amagnetic element 224 toactuatethe movable contact 222,magnetic element 224 being mechanically connected to an air dashpot 226.Movable contact 222 is biased normally to open the circuit through thecontacts22t1 and 222 by means of a tension spring 228. Thus, spring 228biasesV the contacts 222 and 220 into open configuration whereas airdashpot 226 opposesthis action in order to delay opening of the contactsfor a short time interval after a deenergization of coil 218. As will berecognized, a failure in theV periodic closing, of contacts 188 and 190opens theV circuit from line 50h, through wire 186, wire 184 and coil218 to the line 48b. Upon deenergization of coil 218 in this manner,spring 228 eventually overcomesthe mechanical resistance of dashpot 226to open the contacts 220 and 222., This opening of the circuit throughcontacts 220 and 222V in effect opens the circuit to the coil of relay42b to which contact 222V is connected by aV wire23fi.V A wirev 232connects the movable contact of relay 42b. to; the, line Sib.

While the preferred embodiments of theV present invention have beenshownand described herein, it-v is obvious thatmany structural detailsmay bechanged without departing from the spirit/and scope of the appendedclaims.

The invention is claimed as follows:

1. A control system. for a plurality of burners comprising:v valvemeansV forv operating. said burners; relay means for` regulating saidvalve means; circuit means for actuating. said relay means inrresponsevto thecondition of said burners, said circuit meansvincluding aplurality of sensing circuits connected inparallel and.. adapted to beindividually associated with said burners externall to the flamesthereof, each of said sensingcircuits including a sensor adapted to bedisposed adjacent a burner anda switch connected in series with said`sensor; rotatable shaft meansta plurality of cams affixed to said shaftmeans and arranged to operate said switches in a repetitive sequence;and means responsive to the rotation, of said shaftmeans forde-energizing the circuit means upon cessation of rotation of any partof said shaft means.

2. A control system for a plurality of burners comprising: valve meansfor operating saidburners; relay means for regulating said valve means;circuit means for actuating said relay means in response to thecondition of said burners, said circuit means including a plurality ofsensing circuits connected in parallel and adapted to be individuallyassociated with said burners external to the dames thereof, each of saidsensing circuits including a sensor adapted to be disposed adjacent aburner and, a

normally open switch electrically connected in series with said sensor;rotatable shaft means; a plurality of cam means afxed to said shaftmeans and arranged momentarily to close said switches in a repetitivesequence; a power source; and control means connected in circuit betweensaid source and said relay means, including a control switch operated bya cam on said shaft, said control means passing power to said relaymeans when said control switch is regularly and periodically closed bysaid cam, said control means blocking power to said relay means uponinterruption of the periodic operation of said control switch.

3. A control system according to claim 1 wherein said rotationallyresponsive means includes periodically energizable control meansconnected to said circuit means for maintaining said circuit meansconnected to a power Q5 source upon said control means beingperiodically energized, said rotationally responsive means furtherincluding means periodically operated upon rotation of said shaft meansfor periodically energizing said control means.

References Cited in the tile of this patent UNITED STATES PATENTS2,291,385 Gossett July 28, 1942 2,295,045 Mettler Sept. 8, 19422,304,200 Plein et al. Dec. 8, 1942 2,327,690 Ackerman Aug. 24, 19432,581,942 Collins et al Jan. 8, 1952 2,692,962 Thomson Oct. 26, 19542,736,371 Rafenstein Feb. 28. 1956

1. A CONTROL SYSTEM FOR A PLURALITY OF BURNERS COMPRISING: VALVE MEANS FOR OPERATING SAID BURNERS; RELAY MEANS FOR REGULATING SAID VALVE MEANS; CIRCUIT MEANS FOR ACTUATING SAID RELAY MEANS IN RESPONSE TO THE CONDITION OF SAID BURNERS, SAID CIRCUIT MEANS INCLUDING A PLURALITY OF SENSING CIRCUITS CONNECTED IN PARALLEL AND ADAPTED TO BE INDIVIDUALLY ASSOCIATED WITH SAID BURNERS EXTERNAL TO THE FLAMES THEREOF, EACH OF SAID SENSING CIRCUITS INCLUDING A SENSOR ADAPTED TO BE DISPOSED ADJACENT A BURNER AND A SWITCH CONNECTED IN SERIES WITH SAID SENSOR; ROTATABLE SHAFT MEANS; A PLURALITY OF CAMS AFFIXED TO SAID SHAFT MEANS AND ARRANGED TO OPERATE SAID SWITCHES IN A REPETITIVE SEQUENCE; AND MEANS RESPONSIVE TO THE ROTATION OF SAID SHAFT MEANS FOR DE-ENERGIZING THE CIRCUIT MEANS UPON CESSATION OF ROTATION OF ANY PART OF SAID SHAFT MEANS. 